The Neuronal Monoamine Transporter VMAT2 Is Regulated by the Trimeric GTPase Go₂

Abstract

Monoamines such as noradrenaline and serotonin are stored in secretory vesicles and released by exocytosis. Two related monoamine transporters, VMAT1 and VMAT2, mediate vesicular transmitter uptake. Previously we have reported that in the rat pheochromocytoma cell line PC 12 VMAT1, localized to peptide-containing secretory granules, is controlled by the heterotrimeric G-protein Go(2). We now show that in BON cells, a human serotonergic neuroendocrine cell line derived from a pancreatic tumor expressing both transporters on large, dense-core vesicles, VMAT2 is even more sensitive to G-protein regulation than VMAT1. The activity of both transporters is only downregulated by Galphao(2), whereas comparable concentrations of Galphao(1) are without effect. In serotonergic raphe neurons in primary culture VMAT2 is also downregulated by pertussis toxin-sensitive Go(2). By electron microscopic analysis from prefrontal cortex we show that VMAT2 and Galphao(2) associate preferentially to locally recycling small synaptic vesicles in serotonergic terminals. In addition, Go(2)-dependent modulation of VMAT2 also works when using a crude synaptic vesicle preparation from this brain area. We conclude that regulation of monoamine uptake by the heterotrimeric G proteins is a general feature of monoaminergic neurons that controls the content of both large, dense-core and small synaptic vesicles.

Overexpression of the Drosophila vesicular monoamine transporter increases motor activity and courtship but decreases the behavioral response to cocaine

“…[68][69][70]74,75 Furthermore, these results suggest that relatively modest changes in the expression of mammalian VMAT orthologs could have behaviorally significant effects relevant to psychiatric illness. Although no change in VMAT2 expression was detected in patients suffering from Tourette's syndrome or OCD, 76 children with ADHD show a decrease in VMAT2 levels on platelets.…”

Vesicular monoamine transporter 2 regulates the sensitivity of rat dopaminergic neurons to disturbed cytosolic dopamine levels

“…In addition, posttranslational modifications of VMAT2, e.g. phosphorylation, have been shown to increase electrically-evoked dopamine release (Pothos, 2002), and co-incubation with vesicular small heterotrimeric G-proteins to decrease neurotransmitter uptake (Holtje et al, 2000;Holtje et al, 2003), suggesting various pathways for regulation of VMAT2 activity. Thus, enhancing VMAT2 expression and/or activity in disorders characterized by dysregulated dopamine homeostasis, such as Parkinson's disease, could exert a neuroprotective function by lowering dopaminedependent oxidative stress.…”

Mitochondrial Complex I Inhibitor Rotenone Inhibits and Redistributes Vesicular Monoamine Transporter 2 via Nitration in Human Dopaminergic SH-SY5Y Cells

“…Dopamine Uptake. Dopamine uptake was measured essentially as reported previously (Höltje et al, 2000) but with minor modifications. In brief, the medium was removed, and cells were washed twice with PBS and once with potassium glutamate buffer (KG buffer) containing 150 mM potassium glutamate, 20 mM 1,4-piperazine diethanesulfonic acid, 4 mM EGTA, and 1 mM MgCl 2 adjusted to pH 7.0 with KOH, before being suspended in KG buffer.…”